The field of the present invention is heat transfer catheters for heating and cooling body fluid.
The advantageous use of hypothermia in medical procedures is known. For example, a reduction in metabolic rate of a body may be achieved through the lowering of body temperature. Reduced metabolism makes it possible to more easily accommodate lengthy operative procedures. In stroke, trauma and several other pathological conditions, hypothermia also reduces the permeability of the blood/brain barrier. It inhibits release of damaging neurotransmitters and also inhibits calcium-mediated effects. Further, hypothermia inhibits brain edema and lowers intracranial pressure. Improvements have been observed for patients suffering from severe brain trauma or from ischemia caused by stroke or heart attack when the patient is cooled below normal body temperature (38xc2x0 C.).
Hypothermic treatment has been typically addressed systemically, meaning that the overall temperature of the entire body is lowered. A cooling device used systemically in the circulatory system is known to be more efficient than external methods such as cooling blankets, ice water, bladder lavages, ice baths, esophageal catheters since the entire volume of the body is constantly perfused with the cold fluid at a capillary level.
In other medical situations, it may be desirable to raise the patient""s body temperature. For example, a patient may suffer from unintended hypothermia and may need to be warmed to a normothermic temperature. These results can be obtained by intravascular heating through a heat exchange catheter.
Heat exchange catheters are also used to create hypothermia and hyperthermia in a patient or in selected portions of the patient""s body. Systems capable of such operation are illustrated by Gobin et al. in U.S. Pat. No. 6,126,684, the disclosure of which is incorporated herein by reference.
As understood by the present invention, cooling blankets, lavages and the like are cumbersome and time consuming to use and manage. The present invention provides the solutions noted below.
The present invention is directed to catheters adapted to exchange heat with a body fluid flowing through a body conduit. The catheters employ at least one elongate lumen forming multiple turns for heat transfer with the body fluid.
In a first separate aspect of the present invention, the catheter shaft includes an axis, a fluid inlet lumen and a fluid outlet lumen each extending generally between a proximal end and a distal end of the shaft. A hub disposed at the proximal end provides access to the fluid lumens. At least one balloon is provided in a heat exchange region at the distal end of the shaft, the balloon wall providing the barrier between the two fluids. With the catheter positioned in contact with the body fluid within the conduit, heat transfer occurs across the balloon wall. The relative temperature differential is facilitated with countercurrent flow between the two fluids.
In a second separate aspect of the invention, a first balloon is disposed at the distal end of the shaft and defines with the shaft an inflatable first cavity. Portions of the shaft define a first inlet hole extending in fluid communication between the first lumen and the first cavity. Portions of the shaft define a first outlet hole extending in fluid communication between the first cavity and the fluid outlet lumen. A second balloon disposed relative to the first balloon defines with the shaft an inflatable second cavity with portions of the shaft defining a second inlet hole between the fluid inlet lumen and the second cavity. Portions of the shaft also define a second outlet hole in fluid communication with the second cavity and the fluid outlet lumen. Typically, the first balloon will be disposed distally of the second balloon and the first inlet hole will be larger than the second inlet hole. As elastomeric material covering a valley or volume between the first balloon and the second balloon may be provided to promote mixing necessary for efficient heat exchange yet minimize turbulence and shear which can be damaging to blood.
In a third separate aspect of the invention, a method for exchanging heat with a body fluid in a body conduit includes the step of introducing into the body conduit a catheter having an inlet lumen and an outlet lumen. The catheter is provided with a first cavity and a second cavity each in heat transfer relationship with the body fluid in the body conduit. A heat exchange fluid is introduced into the inlet lumen and through an inlet hole into each of the first cavity and the second cavity. An exchange of heat then occurs between the heat exchange fluid in the first and second cavities and the body fluid in the body conduit. Ultimately, the heat exchange fluid is removed through an outlet hole and the outlet lumen associated with each of the first cavity and the second cavity. Creating non laminar flow in one or both of the heat exchange fluid and the body fluid will improve heat transfer efficiency. Heat transfer can also be effected by various structures which either enhance or inhibit turbulence in the fluids.
In a fourth separate aspect of the present invention, the elongate lumen forms multiple turns with the turns each having a length and being bonded to the catheter along a fraction of that length. The length of the lumen and its orientation in each turn has the lumen otherwise displaced from the elongate body. Thus, body fluid can flow freely about each turn of the lumen with the exception of the fractions of length where the lumen is attached to the catheter.
In a fifth separate aspect of the present invention, the elongate lumen is helical and forms multiple turns and extends longitudinally along a portion of the catheter. The length of the lumen and its orientation in each turn has the lumen otherwise displaced from the elongate body. Thus, body fluid can flow freely about each turn of the lumen with the exception of the fractions of length where the lumen is attached to the catheter.
In a sixth separate aspect of the present invention, the elongate lumen is displaced over a major portion of its length from the body of the catheter. The turns of the lumen can be arranged in sets having different lengths to encounter all areas of the flow.
In a seventh separate aspect of the present invention, the elongate lumen is principally displaced from the catheter body for efficient body fluid flow about the lumen. One or more infusion lumens may also extend to an infusion port or ports, advantageously operating with the helical elongate lumen to better distribute infusions within the stream of the body fluid.
In an eighth separate aspect of the present invention, the elongate lumen is defined by an elongate element principally displaced from the elongate body of the catheter. The elongate element is thin-walled and collapsible under fluid pressure of the body fluid when the flow through the lumen is not induced. The thin-wall provides flexibility for an initially collapsed position of the helical elongate lumen for insertion, its expansion under pressure and subsequent and partial collapse for extraction and provides efficient heat transfer across the wall of the element.
In a ninth separate aspect of the present invention, the elongate lumen, defined by an elongate element forming a helical and axially extending configuration, is principally displaced from the elongate body of the catheter for fluid body flow about the lumen along most of its length. The body of the catheter includes an input lumen and an output lumen in fluid communication with the helical elongate lumen. The elongate element defining the helical elongate lumen has a substantially equal cross-sectional area to that of the input lumen such that the elongate element can be fitted with the input lumen.
In a tenth separate aspect of the present invention, the elongate lumen is arranged to be displaced along a substantial portion of its length from the catheter. This lumen is in fluid communication with a heater/chiller supplying a working fluid for heat transfer through the wall of the elongate element defining a helical elongate lumen. A proximal hub may be associated with the catheter to establish at least one suture anchor. Further, the hub may receive the heater/chiller flow through input and output lumens associated with the catheter and in fluid communication with the helical elongate lumens.
In an eleventh separate aspect of the present invention, a method for treating cardiac arrest in a patient is contemplated.
In a twelfth separate aspect of the present invention, a method for treating myocardial infarction in a patient is contemplated.
In a thirteenth separate aspect of the present invention, combinations of any of the foregoing aspects and features are contemplated.
Accordingly, it is an object of the present invention to provide improved heat transfer catheters. Other and further objects and advantages will appear hereinafter.